Which of the following represents the approximate diameter reduction of the internal carotid artery (ICA) when evaluating the spectral waveform and peak systolic velocity (PSV) and end-diastolic velocity information?

The approximate diameter reduction of the internal carotid artery is represented by the spectral waveform and peak systolic velocity (PSV) and end-diastolic velocity information. Options A, B, and D are incorrect. These options represent a smaller percentage reduction in diameter of the internal carotid artery compared to option C. A 25-49% reduction would still allow for adequate blood flow, while a 100% reduction would result in complete blockage of the artery. Option C, representing an 80-99% reduction, is a more clinically significant and accurate representation of the diameter reduction of the internal carotid artery when evaluating spectral waveform and velocity information.